APRS-IS is used to transport data that did not originate on RF and should
not be gated to RF, some CWOP weather system reports for example.

There is a newer APRS-IS network called "APRS2" which offers alternative APRS-IS servers available at: http://www.aprs2.net/

Once APRS packets make it through an igate to the internet system, they get recorded in various databases that are then searchable. This is an excellent way sometimes of examining and improving your station, assuming your packets are making it to an igate that is. Here are a few of these sites: